1. Field of the Invention
This invention pertains to a pressure fluid operated metering pump having an improved pneumatic control system mounted directly on the pump body and incorporated partially in an improved pneumatic circuit manifold assembly.
2. Background Art
The above referenced patent application discloses a pressure fluid operated metering pump having a power piston comprising a rolling diaphragm mechanically connected to a pump piston also of the flexible diaphragm type. The pump control mechanism disclosed in the above referenced patent application includes a control circuit which utilizes a fluid operated spool valve for delivering fluid pressure pulses to the working piston of the pump and for exhausting the working piston expansion chamber. The fluid operated valve is controlled by an electrically energized valve operator which in turn is controlled by an electronic pulsing circuit.
In many applications of metering pumps the pump is situated in a hazardous environment created by the pumped fluid being a volatile substance or the application of the pump being in the vicinity of explosive gases or liquids. Moreover, in many applications of metering pumps and the like it is desirable and advantageous to utilize the working fluid to operate the pump control components to simplify the pump installation requirements. It is particularly advantageous to utilize the working fluid as a controlling medium if the fluid is compressed air or other compressed gases.
There are also advantages in certain applications of metering pumps to utilize a working fluid which may be a toxic or explosive gas and, accordingly, it is important to be able to eliminate any electrical components in the vicinity of the pump and be able to provide for conducting the spent working fluid into an exhaust conduit or chamber to avoid venting the working fluid to atmosphere.
Many applications of metering pumps require a very wide range of discharge flow rates. Electrical circuitry required to meet the desired range of flow rates for metering pumps becomes unduly complicated and expensive and, accordingly, pressure fluid controls are advantageously used for applications requiring a wide range of flow rates. In this regard also it is important in many pump applications to have a control system which will operate with a working fluid and a control fluid wherein the fluid pressures may vary considerably.
It is, of course, desirable that metering pumps be as compact and inexpensive to manufacture as practical. In this regard it is noted that many prior art pumps do not have a compact control system which is adapted to be mounted directly on the pump itself and is entirely self contained to minimize fluid conduit interconnections and the like which contribute to fluid leakage and the problems attendent thereto.